Generally, pneumatic tires are required to have so high performance as to meet multiple performance requirements at the same time. It is strongly desirable to have tire members such as treads, among others, that can reduce the rolling resistance of the tires and are excellent in abrasion resistance. There is a tradeoff between these properties, however, which have necessitated years and years of trial and error to date.
Rubber compositions applied to tire treads use hydrous silicate as a reinforcing filler. In general, as the content of hydrous silicate increases, the abrasion resistance of the tire improves to some extent, yet the rolling resistance may deteriorate. In some cases, the viscosity of unvulcanized rubber increases more than is required, which may result in reduced workability.
Under such circumstances, silane coupling agents have been developed to solve the aforementioned problem, but a sufficient degree of silica dispersion has not been achieved yet, which makes it difficult to provide good dispersion of silica particles in industrial terms.
Thus, in order to obtain further improved dispersibility of silica, JPH06248116A (PTL 1) discloses a technique for promoting reaction of a silane coupling agent by kneading therewith silica particles having surfaces treated with a hydrophobizing agent.
In addition, WO2009091057A1 (PTL 2) discloses a technique for improving the abrasion resistance and reinforcing capability of a rubber composition by including hydrous silicate with a particular structure contained in the rubber composition.